The objective of the Clinical Core is to provide the clinical resources for the individual research projects within the Sexually Transmitted Infections Cooperative Research Center (STI CRC). The Clinical Core will assemble a cohort of 250 women with acute PID to participate in a randomized controlled trial of two antibiotic regimens for the treatment of acute PID (Project 1). This cohort will also serve as the source for specimens for Project 2, examining novel previously uncultivatable organisms in endometritis. The Clinical Core will also construct a cohort of 200 women with or at-risk for Chlamydia trachomatis infection to determine the antigen-specific cell mediated immune resposes that are most strongly associated with protection against C. trachomatis infection and to elucidate the antigen specifc immune responses correlated with containment of C. trachomatis infection to the lower genital tract (Project 4). To accomplish its goal of recruiting participants and collecting specimens to meet each of the projects' goals, the Clinical Core has assembled reecruitment sites that are the major providers of reproductive health care in our region, and are sites that are successful in the conduct of STI research. The Clinical Core will perform the vaginal and endometrial cultures and the STI diagnostic testing in support of Projects 1, 2 and 4. The Clinical Core personnel consists of a physician research, a PhD microbiologist, two nurse practitioners and research assistants who have extensive experience in STI research and the conduct of large clinical trials. By using a single research team and a network of clinical sites with provien ability to recruit participants for STD research, the Clinical Core will be able to successfully recruit research participants to meet the individual needs of the projects of this STI CRC application.